The BBC has played down reports that two Blue Peter "viewers" chosen to meet Dead Ringers star Jon Culshaw were actually supplied by a drama group.

Viewers were asked to submit questions to the comedian via the show's website in September 2005.

But two of the six children picked came from a local drama group.

The BBC said it often used unpaid volunteers from drama groups, but the show should have made clear that not all the children came via the website.

It added that none of the children had been paid, they were not members of Equity, the item was not a competition, and that no prizes were offered or awarded.

Richard Deverell, controller of BBC children's programmes, said: "Our presenter should have made it clear that only some of the children on the show came via the website."

But he explained it was "standard practice" for producers to form relationships with local schools and drama groups to help pad out audiences and to help prevent other children featured on the programme from being too shy to contribute.

"It's something which we'll keep on doing because we need articulate, confident children who will contribute something to our shows," Mr Deverell said.

Cat name

The episode follows two recent incidents which Blue Peter admitted it had misled viewers.

The hosts of Blue Peter apologised to viewers on air in September about the rigging of a poll to name the show's cat.

The cat was named Socks after the results of an online poll were changed. Viewers of the BBC One show had wanted to call the cat Cookie.

In November 2006, a child visiting the Blue Peter studio was asked to pose as a competition caller, and won a prize.

The programme was fined £50,000 by media watchdog Ofcom over the incident.